sub DEBUG {
    0;
}
sub SymRef {
    'My::Package::hash';
}
sub PI {
    3.141592;
}
if (DEBUG ) {
    warn "Okay, we are debugging...\n";
    do_lots_of_debugging_stuff ;
}
$My::Package::hash{'key'} = 'value';
print SymRef()->{'key'}, $/;
print PI() + 5, $/;
- syntax OK